1. Field of the Invention
The present invention relates generally to a multi-ballast lighting and control system, and, more particularly, to a distributed intelligence multi-ballast lighting system employing a DALI backward compatible extended protocol for messages in a lighting control network that extends the functionality of the lighting control network.
2. Description of Related Art
In recent years, large-scale lighting systems have been developed to meet the needs of lighting applications with distributed resources and centralized control. For example, building lighting systems are often controlled on a floor by floor basis or as a function of the occupancy space used by independent groups in the building. Taking a floor of a building as an example, each room on the floor may have different lighting requirements depending on a number of factors including occupancy, time of day, tasks ongoing in a given room, security and so forth, for example.
When a number of rooms are linked together for lighting purposes, control of lighting in those rooms can be centralized over a network. For example, while power to various lighting modules can be supplied locally, control functions and features of the lighting system can be directed through a control network that sends and receives messages between a controller and various lighting system components. For instance, a room with an occupancy sensor may deliver occupancy-related messages over the network to inform the controller of the occupancy condition of the given room. If the room becomes occupied, the lighting controller can cause the lighting in that room to turn on, or be set to a specified dimming level.
When messages are exchanged in the lighting control network, a protocol is employed to permit the various network components to communicate with each other. One popular protocol presently in use is the Digital Addressable Lighting Interface (DALI) protocol. The DALI protocol represents a convention for communication adopted by lighting manufacturers and designers to permit simple messages to be communicated over a lighting network in a reasonably efficient manner. The DALI protocol calls for a 19 bit message to be transmitted among various network components to obtain a networked lighting control. The 19 bit message is composed of address bits and command bits, as well as control bits for indicating the operations to be performed with the various bit locations and the message. For example, one type of message provides a 6 bit address and an 8 bit command to deliver a command to the addressed network component. By using this protocol technique, sixty-four different devices may be addressed on the lighting network to provide the network control. A large number of commands can be directed to the addressable devices, including such commands as setting a power on level, fade time and rates, group membership and so forth.
A conventional ballast control system, such as a system conforming to the DALI protocol, includes a hardware controller for controlling ballasts in the system. Typically, the controller is coupled to the ballasts in the system via a single digital serial interface, wherein data is transferred. A disadvantage of this single interface is that the bandwidth of the interface limits the amount of message traffic that can reasonably flow between the controller and the ballasts. This can also create delays in times to commands.
In the present day DALI protocol, a portion of the command space is set aside for future functionality, or for adaptation by individual users. However, the reserved command space provides limited additional functionality due to the relatively small number of commands available in the space that is set aside. In addition, it is less desirable to use the reserved command space for customized network lighting applications, due to problems with interoperability. For example, if different manufacturer components are used on a DALI lighting network, and the components expect to use a command in the reserved command space for different purposes, the lighting network would operate improperly due to the conflict in the command space.
More recently, lighting designers have demanded greater functionality from lighting networks to realize improved features in the operation of a lighting system. For example, the lighting designer may desire that a number of lighting components may be located in a single room, each of which may require an address. One simple example is a room that includes multiple ballasts for control of fluorescent lamps, a photosensor to determine the amount of light in the room, an occupancy sensor, and a control station. It is desirable to have these components provided over one single lighting control network.
As more and more demands are placed on the lighting control network to increase the functionality of the lighting system, the DALI protocol becomes limited in its ability to handle a wide variety of commands, even when the reserved command space is utilized. In addition, the addressing arrangement in the DALI protocol is limited to 64 addresses for each DALI controller. As more lighting devices are connected to a DALI network, additional DALI controllers are needed because of the limited address space. With a large number of DALI controllable devices in a building, a number of DALI controllers are used and a building control system or network is connected to the DALI controllers to provide further extendibility and flexibility in the lighting control for the building. Such an arrangement can become increasingly expensive and fault intolerant as more and more devices are added to each DALI network.
Another feature of the DALI controller used in DALI protocol networks is that the controller supplies power to all devices on the network, as well as control and query commands. One drawback of this arrangement is observed if the DALI controller fails, meaning the loss of the power bus as well as the command/control bus. Accordingly, if the controller fails, the entire lighting system will be non-functional.
Another operation for the DALI protocol that tends to reduce response time is the polling of devices in the DALI bus. For example, if an occupancy sensor is to be used to turn on a ballast through the DALI network, the DALI controller polls the sensors in the DALI network to determine when an event occurs to indicate a change in the occupancy of a room, meaning the associated ballast should be energized. The process for polling the devices on the DALI bus can be somewhat time intensive, because polling commands may be supplied for each device on the DALI bus in a cyclical fashion, so that the latency for a given occupancy sensor to indicate a change in status may be significant. In effect, the control for the entire DALI network is centralized through the DALI controller, so that control is effected through processing and communication from a central point.
Another aspect of devices that are used on a DALI network is the fact that the components must include communication ports for connection to the DALI bus, and be able to communicate with a DALI controller. Accordingly, the devices are inherently more complex than traditional devices that are not connected to a network. The complexity of the components can significantly increase the cost of a DALI controlled lighting network.